Photographic silver halide emulsions containing trifluoromethyl - 4 - hydroxy quinoline carboxy acid salt as a stabilizer



United States Patent 3,446,618 PHOTOGRAPHIC SILVER HALIDE EMULSIONS CONTAINING TRIFLUOROMETHYL 4 HY- DROXY QUINOLINE CARBOXY ACID SALT AS A STABILIZER Fritz Dersch, Binghamton, and Sally L. Paniccia, Endwell, N.Y., assignors to GAF Corporation, New York, N .Y., a corporation of Delaware No Drawing. Filed Nov. 8, 1965, Ser. No. 506,840 Int. Cl. G031: 5/24, 1/34 US. Cl. 96-665 11 Claims ABSTRACT OF THE DISCLOSURE Stabilization of light-sensitive silver halide emulsions by incorporation therein or in a developer used to process the same, of a trifluoromethyl-4-hydroxy quinoline carboxy acid salt or ester amounting to 1 to 40 mg. per mole of silver halide or 1 to 50 mg. per liter of developer solution.

The present invention relates in general to the provision of novel additives for improving the sensitivity, contrast, covering power, etc. of photographic silver halide emulsions and in particular to the employment of certain quinoline derivatives for such purposes.

As is well known, the sensitivity of light-sensitive silver halide emulsions can be increased in a number of ways as for example by the incorporation therein of one or more chemical or optical sensitizing agents which function to augment and/or extend the emulsion sensitivity to light of longer wave lengths.

In general, it is postulated that chemical sensitization results from the formation of small amounts of silver sulfide and/or silver on the surface of the silver halide crystal. As examples of compounds found to function as chemical sensitizing agents there may be mentioned sodium sulfite, sodium thiosulfate and the like.

Heretofore, a wide variety of compounds has been suggested for purposes of increasing the spectral sensitivity of photographic silver halide emulsions. Particularly beneficial results are purportedly obtained with such compounds as the polyoxyalkylene ethers and numerous derivatives thereof such as the products obtained by reacting alkylene oxide with reactive hydrogen-containing organic compounds, e.g., acids, alcohols, amines, etc. The use of the foregoing and related compounds for such purposes is well established in the prior art being extensively described in the patent and trade literature. Other compounds proposed for use in a similar relationship include the quarternary ammonium, phosphonium and ternary sulfonium salts as well as combinations or mixtures of one or more of the foregoing compounds with alkylene oxide polymers.

Other problems frequently encountered in the emulsion-making as well as the emulsion-processing industries relate to the production of relatively high speed emulsions which enable the attainment of image reproductions characterized by satisfactory contrast as wellas covering power of the developed silver. As is well known, the term covering power is a measure of the silver concentration in the developed image and is derived arithmetically by dividing the optical density at maximum density by the grams of silver per square decimeter in the developed image layer.

As examples of materials heretofore promulgated for use as emulsion addenda to thereby obtain the requisite contrast, silvercovering power, etc., there may be mentioned in particular the poly-N-vinyl lactams, the watersoluble polyglucose dextrans, water-soluble S-hydroxyalkyl ethers of polyvinyl alcohol, water-soluble hydroiyzed glycogen, water-soluble mannan polysaccharide, the Water-soluble polyglucose laminarins, hydroxy-ethyl cellulose, carboxymethylated proteins and the like.

While the foregoing and related compounds have been found in the vast majority of instances to provide some measure of improvement their use is invariably accompanied by other significant drawbacks which tend to detract considerably from their desirability. For example, many of the foregoing compounds must of necessity be employed in inordinately large proportions resulting in a depression of the melting point of the emulsion layer which, in turn, leads to such undesirable defects as reticulation, the latter becoming particularly manifest in those instances wherein the emulsion is subjected to high temperature, rapid processing. Moreover, such compound can present serious problems of fog and especially when the emulsion containing same is stored for any significant period of time under severe conditions of temperature and/or humidity. A further deterrent to the use of the compounds thus far known resides in their pronounced tendency to cause turbidity either in the wet or dry state of the emulsion layer.

In an effort to overcome or otherwise alleviate the foregoing and related disadvantages, considerable industrial research and development has centered around the pro vision of compounds which, when incorporate-d into lightsensitive silver halide emulsion layer, impart thereto acceptable photographic speed, contrast and covering power while reducing substantially any tendency of the silver halide emulsion in fog. However, despite the extensive industrial effort in this regard, the compounds thus far suggested have been found, characteristically, to provide a satisfactory measure of improvement only at the expense of other essential emulsion properties.

Thus, a primary object of the present invention resides in the provision of improved light-sensitive silver halide emulsions as well as photographic elements fabricated therewith in which the above and related disadvantages are eliminated or at least mitigated to a substantial extent.

A further object of the present invention resides in the provision of improved light-sensitive silver halide emulsions characterized by outstanding improvement in photographic speed, contrast and covering power of the silver image developed therein.

A still further object of the present invention resides in the provision of improved light-sensitive silver halide emulsion substantially devoid of any tendency to fog and further characterized by outstanding stability even under conditions of high temperature and/or humidity.

Other objects and advantages of the present invention will become apparent hereinafter as the description thereof proceeds.

The attainment of the foregoing and related objects is made possible in accordance with the present invention which, in its broader aspects, provides bringing into operative association with the light sensitive photographic emulsion, a quinoline derivative of the following general formula:

COOR F30 Rx wherein R represents hydrogen, lowr alkyl of l to 4 carbon atoms, e.g., methyl ethyl, propyl, etc. or a watersolubilizing cation, and R represents hydrogen or lower alkyl. It will be further understood that the phenylene nucleus in the above formula may further contain one or more inert substituents including for example, lower alkyl, lower alkoxy, e.g., methoxy, ethoxy, etc.; hydroxyalkyl, e.g., hydroxyethyl; halogen, e.g.. chloro, bromo, etc. As examples of suitable water-solubilizing cations there may be mentioned the alkali metals, e.g., sodium, potassium; ammonium; substituted ammonium, in which one or more of the hydrogens is replacedby lower alkyl, e.g., methyl, ethyl, propyl, etc.; hydroxy lower alkyl, e.g., hydroxy ethyl, and wherein such substituents may be the same or different.

In accordance with the discovery forming the basis of the present invention, it has been ascertained that silver halide emulsions of reduced fog, increased speed, contrast, and covering power of the developed silver can be obtained by including one or more of the compounds encompassed by the above formula in the light-sensitive silver halide layer, an undercoating, an intermediate coating, an overcoating and/or a surface coating. The concentrations employed are not particularly critical so long as sufficient amounts be present to impart to the emulsion the desired characteristics. Thus, the quinoline derivative may be advantageously employed in concentrations varying over a relatively wide range and preferably from about 1 to about 40 milligrams per mole of silver halide.

\Vithin the aforesaid range, the amount selected will depend upon a variety of factors including for example the type of emulsion used. With emulsions of the high speed ammonia type, it is found that the use of 8 to milligrams of the above described quinoline derivative per mole of silver halide is particularly beneficial. Furthermore, in those embodiments wherein the quinoline compound is incorporated int-o a non-sensitized auxiliary layer, e.g., anti-abrasion layer, undercoating, etc., it is usually preferred that such quinoline derivative be utilized in the higher concentration range. In this manner, it is assured that a sufficient amount of the quinoline compound will be brought into operative association with the sensitized emulsion layer to thereby realize the improvements contemplated herein. Without intending to be bound by any theory, it has been postulated that the quinoline compound diffuses or otherwise migrates to the sensitized emulsion layer thus bringing about the desired intimacy of contact.

When added to the emulsion layer, it is preferred that the addition be made during the actual preparation of the emulsion, either before or after the emulsion washing step.

The improved anti-fogging and stabilizing elfects made possible by the present invention may also be obtained according to a further embodiment by including the quinoline derivative in the developer solution and/or alkaline pre-bath, i.e., such that the development'operation will be effected in the presence of such compound. -In such instances, the quinoline derivative may be employed in concentrations ranging from about 1 to about 50 milligrams per liter of solution, with a range of about 5 to about milligrams per liter being particularly preferred.

The quinoline derivatives encompassed by the abovedepicted structural formula are known compounds and are readily available commercially. Suitable methods for their preparation are described in standard reference works on the subject and in this connection particular reference is made to the procedures described in for example, J.A.C.S., 69, pp. 371-7-4 (1947) and I.A.C.S., 71, pp. 3507-08 (1949).

Perhaps the salient advantage presented by .the use of the above described quinoline derivatives relates to the fact that the speed of the photographic emulsion is in no way deleteriously affected notwithstanding the use of the quinoline compound in relatively large amounts. Such compounds are of exceptional value as anti-fogging agents, and since little in the way of limitation is imposed as regards the concentrations employed significant increases in t e ph qsr p c sp ed and co t as of he e u s on as well as the covering power of the developed image are readily obtained despite the use of proportions which would ordinarily, i.e., with the compounds heretofore provided in the art, result in severe fogging. In addition, it is found that the desired emulsion characteristics are obtained even under conditions of high temperature processing such as those required with the use of modern processing machines. The rather limited properties characterizing the stabilizer compounds thus far provided in the photographic art has necessarily imposed severe limitations upon the adaptability of photographic elements containing same to high speed machine processing.

Accordingly, it is of paramount commercial significance that photographic elements prepared with the quinoline derivatives of the present invention are eminently suitable for such high speed machine processing in the virtual absence of fog, loss of speed, etc.

The following examples are given for purposes of illustrating the present invention only and are not to be regarded in any way as being limitative thereof:

EXAMPLE I This example illustrates the use of 3-carboxy-4-hydroxy-7-trifluoromethyl quinoline which is prepared according to the method described in 'J.A.C.S., 69, pp. 371- 74 (1947).

A silver halide emulsion in gelatin containing 4% silver iodide and 96% silver bromide was prepared in a conventional manner and brought up to its maximum light sensitivity. It was then readied for coating on film base, that is, melted at 40 C.; necessary coating finals were added such as sensitizing dyes, stabilizers and hardeners. Approximately 8 cc. of a 0.1% solution of 3-carboxy-4-hydroxy-7-trifluoromethyl quinoline in methanol was added to a sample of the above-described emulsion containing about 0.6 mol of silver halide. A sample of the same emulsion, but not containing the quinoline compound served as a control. The so prepared emulsion samples were coated on a cellulose ester base and dried. Samples of these film coatings were then exposed in a Type IB Sensitometer and developed in a developer of the following composition:

Metol grams 1.5 Sodium sulfite, anhydrous do 45 Sodium bisulfite do 1 Hydroquinone do 3 Sodium carbonate, monohydrated do 6 Potassium bromide do 0.8 Water to make liter 1 Quantity of compound used per 0.6 mol of silver halide Relative speed Dmnx. Fog, 12 dev EXAMPLE II Relative speed Dmax. Fog, 12 dcv.

EXAMPLE III The following example illustrates the improvements made possible by the present invention with photographic elements containing the novel quinoline additives when processed on high speed apparatus.

A silver halide emulsion in gelatin containing 2% silver iodide and 98% silver bromide was prepared in a conventional manner and brought up to its maximum light sensitivity. It was then readied for coating as described in Example I. Test and control samples were prepared as in Example I. Following exposure in a Type IB Sensitometer, each of the samples was developed in an Eastman Kodak M4 X-Omat processing apparatus. The following results were obtained:

Quantity of compound used Relative speed Fog Din. Ag. g./dm.

covering power.

EXAMPLE IV A silver halide emulsion containing 2% silver iodide and 98% silver bromide was prepared. Samples containing about 0.4 mole of silver halide were taken and experiments conducted as follows:

(a) coated as control and provided with a 4 surface coating prepared from 20 grams gelatin in 1 liter water.

(b) as (a) but to the 1 liter of surface solution was added 15 grams of propylene oxide treated gelatin (prepared as described in copending patent application, Ser. No. 319,969, filed Oct. 30, 1963) now Pat, No. 3,312,553.

(0) like (b) but to the emulsion sample were added 8 mg. of 3-carboxy-4-hydroxy-7-trifluoromethyl quinoline.

The test samples (a), '(b), and (0) were sensitometrrcally exposed and developed in an M4 X-Omat apparatus (Eastman Kodak) with the following results:

Covering power,

Experiment Speed Fog Max. Ag. gJdm. Dina... g. gJdm.

Again, the above results clearly demonstrate the synergistic results provided by the novel quinoline additives of the present invention. Of primary importance is the fact that the increase in speed obtained is attended by a minimal fogging level and as clearly demonstrated in Sample (c) there results a marked increase in the silver image covering power.

Results similar to those described above are obtained when the particular quinoline derivatives exemplified are substituted in equivalent amounts and within the proportions specified with the following compounds:

3-carbethoxy-4-hydroxy-7-fluoromethyl-quinoline 2-carbethoxy-3-methyl-4-hydroxy-7-trifluoromethylquinoline 2-carboxy-3-methyl-4-hydroxy-5-trifiuoromethyl-quinoline 2-carbethoxy-3-methyl-4-hydroxy-S-trifiuoromethylquinoline The present invention is not limited to any particular type of light-sensitive silver halide as it is useful with silver chloride, silver bromide, silver iodo bromide, silver chloro bromide, silver iodide, etc., emulsions and mixed emulsions of these types. However, particularly beneficial results are obtained with silver halide emulsions containing on the order of at least mole percent silver bromide with the remainder silver iodide.

The improvements provided by the present invention are not dependent upon the use of any particular type of silver halide developer. Accordingly, the latter may be of the hydroquinone type, i.e., those which contain hydroquinone, potassium metabisulfite and potassium bromide, or they may be of the metol-hydroquinone type, i.e., those which contain p-methylaminophenol, sodium sulfite, sodium bisulfite, hydroquinone, sodium carbonate, and potassium bromide. Alternatively, the developer composition may be of the so-called borax type, i.e., those which contain p-methylaminophenol sodium sulfite, hydroquinone, borax and potassium bromide.

The quinoline derivatives of the present invention may be employed singly or in combination with other sensitizing addenda including for example, the noble metal sensitizers, e.g., gold salts, e.g., chlorauric acid and auric trichloride and, if desired, in association with sulfur sensitizers, e.g., sodium sulfite, thiosinamine, allyl-thiourea, sodium thiosulfate, allyl thiocarbamate, alkali metal thiocyanates and sodium sulfide; these sensitizers can be used in amounts up to 0.005% based on the weight of the silver halide. Moreover, the silver halide emulsions may contain one or more optical sensitizing agents, e.g., cyanine, carbocyanine, merocyanine, pseudocyanine and other cyanine dyes.

The light-sensitive emulsions employed may be those of the type intended for use in color photography, e.g., emulsions containing color-forming components which upon color development with a primary aromatic amino developer yield azomethine quinonimine or azine dyes. Suitable couplers are described in US. Patents 2,186,734, 2,445,252, 2,530,349, 2,671,021, 2,524,725, 2,354,552 and 2,547,037. Furthermore, the color coupler may be of the non-diffusing type which, when added to the silver halide emulsion dispersed in a mixture of high boiling and low boiling solvent form packet-type emulsions with encapsulated color formers. Suitable couplers of the latter type are described for example in US. Patents 2,179,239, 2,179,244, 2,298,443, 2,369,489 and 2,511,231.

The present invention has been disclosed with respect to certain preferred embodiments and they will become obvious to persons skilled in the art, various modifications, equivalents or variations thereof which are intended to be included within the spirit and scope of the present inventron.

What is claimed is: Y

1. A light-sensitive silver halide emulsion containing a stabilizer comprising from 1 to 40 mg. per mole of silver halide, of a compound of the following formula:

wherein R is selected from the group consisting of hydrogen, lower alkyl and a water-solubilizing cation, and R is selected from the group consisting of hydrogen and lower alkyl.

2. A light-sensitive silver halide emulsion according to claim 1 wherein said stabilizer comprises 3-carboxy-4 hydroxy-7-trifluoromethyl quinoline.

3. A light-sensitive silver halide emulsion according to claim 1 wherein said stabilizer comprises 2-carboxy-3- methyl-4-hydroxy-7-trifluoromethyl quinoline.

4. A light-sensitive photographic material comprising a base and at least one light-sensitive silver halide emulsion, said photographic material containing a stabilizer com- COOR wherein R is selected from the group consisting of hydrogen, lower alkyl and a water-solubilizing cation and R is selected from the group consisting of hydrogen and lower alkyl.

5. A light-sensitive photographic material according to claim 4 wherein said stabilizer comprises 3-carboxy-4- hydroXy-7-trifluoromethyl quinoline.

6. A light-sensitive photographic material according to claim 4 wherein said stabilizer comprises 2-carboxy- 3-methyl-4-hydroxy-7-trifluoromethyl quinoline.

7. A light-sensitive photographic material according to claim 4 wherein said stabilizer compound is present in an anti-abrasion layer overcoating said silver halide emulsion layer.

8. A light-sensitive photographic material according to claim 4 wherein said stabilizer is present in a layer positioned intermediate the support and silver halide emulsion layer.

9. A process for the preparation of a photographic silver halide emulsion which comprises forming the emulsion, ripening the emulsion and during said ripening adding thereto a stabilizer comprising from 1 to 40 mg. per mol of silver halide of a compound of the following formula:

10. A process for the preparation of a photographic emulsion which comprises forming the emulsion, ripening the emulsion, coating said emulsion on a base and adding to said emulsion just prior to the coating thereof on the support a stabilizer comprising from 1 to 40 mg. per mol of silver halide, of a compound of the following formula:

liter of developing solution of a compound of the following formula:

0 O O R F30 R1 wherein R is selected from the group consisting of hydrogen, lower alkyl and a water-solubilizing cation, and R is selected from the group consisting of hydrogen and lower alkyl.

References Cited UNITED STATES PATENTS 2,397,015 3/1966 Kendall et a1. 96-107 X 2,578,655 12/1951 Kendall et a1 96109 X 2,948,615 8/1960 Dersch et al. 96--109 3,193,386 7/1965 White 96109 NORMAN G. T ORCHIN, Primary Examiner.

R. E. FICHTER, Assistant Examiner. 

